Performance: Use Lazy initialization wherever possible

[adriangodong]

IEventHandlersRegistry.RegisterEventHandler<T>(T handler) and IEventHandlersRegistry.RegisterWildcardEventHandler<T>(T handler) can user lazy initialization instead of creating a new instance during registration.

IEventHandlersRegistry.RegisterEventHandler<T>(T handler) and IEventHandlersRegistry.RegisterWildcardEventHandler<T>(T handler) can use factory method instead of handler instance input parameter.